The present invention relates to data processing by digital computer, and more particularly to static and dynamic contours.
Portable mapping devices, such as Global Positioning System (GPS) devices and Personal Digital Assistants (PDAs) are capable of displaying and manipulating digital maps. In addition to roads, streets, rivers, lakes and other geographic features, these maps often can display topographical information as well. Topographic maps are also commonly referred to as contour maps or topo maps.
Contour maps show topography, or land contours, using contour lines. Contour lines are curves that connect contiguous points of the same altitude. For example, every point on the marked line of 10 meter (m) elevation is 10 m above mean sea level. To determine differences in elevation between two points on a contour map, the contour interval, or distance in altitude between two adjacent contour lines, must be known, and this is typically given at the bottom of the map. In most cases, contour intervals are consistent throughout a map. Sometimes dashed contour lines are present; these represent half the noted contour interval.
Digital technology enables one to store in a computer and to manipulate a true three dimensional (3D) digital elevation model.